The use of certain vanadium compounds as catalysts for the polymerization of ethylene or the copolymerization of ethylene with alphaolefins and (optionally) nonconjugated polyenes has long been known in the polymerization art. Thus, for example, Natta et al in U.S. Pat. No. 3,260,708 disclose the use of a broad scope of vanadium compounds including vanadium halides; vanadium oxyhalides; vanadyl di- and triacetylacetonates and haloacetyloacetonates; vanadium tribenzoylacetonate; vanadyl trialcoholates and haloalcoholates; the tetrahydrofuranates, the etherates, the aminates of vanadium tri- and tetrachloride and of vanadyl trichloride; and the pyridates of vanadium tri- and tetrachloride and of vanadyl trichloride; as catalysts in the copolymerization of ethylene and aliphatic alphaolefins with certain nonconjugated polyenes. Butcher et al in British Patent 1,403,372 disclose a similarly broad list of vanadium compounds for ethylene polymerization and for ethylene/alpha-monoolefin copolymerization. It is noteworthy that Butcher et al indicate (at page 1, lines 73-74) that "vanadium oxytrichloride is particularly effective" for ethylene copolymerization and ethylene/alpha-monoolefin while Bond, Jr. et al in U.S. Pat. No. 4,022,961 indicate (at col. 5, lines 31-38) that vanadium oxytrichloride is "particularly preferred" as a catalyst for ethylene/alphaolefin/nonconjugated polyene (i.e., "EPDM") polymerization.
While vanadium compound catalysts such as vanadium oxytrichloride (VOCl.sub.3) will, when employed in conjunction with organoaluminum cocatalysts, effectively catalyze the polymerization or copolymerization of ethylene and alphaolefins and/or nonconjugated polyenes, their relatively low efficiency (i.e., the weight of polymer produced per gram of vanadium changed) generally requires a catalyst removal step. This is because a high residual vanadium content in these types of polymers may lead to degradation of such polymers. The removal of vanadium residue from polyolefin polymers is a time-consuming and expensive process. It would therefore be desirable to possess more efficient vanadium catalysts which would produce polymers having a low enough vanadium content that catalyst removal treatment would not be necessary.
U.S. Pat. Nos. 4,189,558 to Witte et al and 4,378,455 to Kawasaki et al both disclose the use of compounds of the formula: ##STR1## wherein R.sub.1 each independently represents hydrogen or C.sub.1 -C.sub.4 alkyl, R.sub.2 each independently represents C.sub.1 -C.sub.4 alkyl, R.sub.3 each independently represents C.sub.1 -C.sub.8 alkyl, and Hal represents chlorine or bromine; in conjunction with trialkylaluminum cocatalysts for the production of strictly alternating copolymers of trans-1,4-butadiene (i.e., a conjugated diene) and propylene. Witte et al discloses that these compounds are produced by reacting vanadium oxyhalides with the corresponding branched alcohols. A similar disclosure is made by Wieder and Witte, Journal of Applied Polymer Science, Vol. 26, pp. 2503-2508 (1981).
However, it is well established that significant differences exist between the copolymerization of conjugated polyenes and that of nonconjugated polyenes. Thus, F. P. Baldwin and G. Ver Strate, "Polyolefin Elastomers Based on Ethylene and Propylene", Rubber and Chemical Technology, Vol. 45, pages 709, 719 (1972) state: "Probably all early workers . . . investigated the use of simple, acyclic conjugated dienes because of price and availability, but it did not take many experiments to decide that these materials were far from adequate for EPDM preparation, catalyst deactivation, . . . being encountered."
Therefore, it has quite unexpectedly been found that certain tert-alkylmethoxy-substituted vanadium compounds will, when employed with certain organoaluminum cocatalysts, function as polyolefin catalysts more efficiently than prior art preferred catalysts such as VOCl.sub.3.